1. Field of the Invention
The present invention relates to a band-shaped and/or a filamentary (wire-shaped) material, which is particularly useful as a solderable electrical conductor. The material of the invention comprises an inner layer of metal, metal alloy, or metal and metal alloy containing phosphorus, specifically between 0.03% and 0.13% by weight of the inner layer, and an outer layer which is a lead alloy. The inner layer may be an alloy such as phosphor bronze, deoxidized copper or similar materials, and the preferred outer layer is a lead-tin alloy. The invention further relates to the use of this material as an electrical conductor.
2. Description of Prior Art
Materials which have an inner layer of a metal and/or metal alloy containing phosphorus and an outer layer containing a lead alloy are used, by preference, in the electric and electronic industries, where solderability and corrosion resistance of the materials are of primary importance. Typically, the inner layer is primarily copper, with amounts of tin and phosphorus also present. The phosphorus content is approximately 0.30 weight percent of the inner layer.
It has been found, however, that materials of this kind age or break down, in the sense that, over the course of time, they lose their moistening power in relation to liquid tin-alloys and/or tin with respect to solderability. Therefore, a particular disadvantage of these known materials is that the aging process including the loss of solderability occurs rather rapidly, with time periods varying from five to twelve weeks being common.